Controller for electric motors



Jan. 13, 1931. E. J. GOVE' 1,789,069

CONTROLLER 1 0R ELECTRIC MOTORS Filed Jan. 2, 1929 My I W ATTORNEYS.

Patented Jan. 13, 1931 UNITED, STATES PATENT ormcs EDWDT I. GOVE, OF YOUNGSTOWN, OHIO, ASSIGNOB BYIMESFI'E ASSIGNMENTS, TO CUT- LEE-HAMMER INC., 01' MILWAUKEE, WISCONSIN, A CORPORATION OF DELAWARE comnonma ron anaemic noroas Application filed January 2, 1829. Serial No. 329,742.

This invention relates to improvements in controllers for electric motors.

In the'control of adjustable speed motors it is frequentl desired to employ a simple I drum or the ike for controlling the continuity of the motor circuit, for reversal,

for speed regulation and for d namic brakin the operator being relie upon to so e ect circuit commutations as to avoid excessive current and voltage conditions. However so much difiiculty has been experienced through careless operation of such controllers that a demand has arisen for one having some effective but yet extremely simple means affording protection against such abnormal conditions as result from too rapid acceleration or too rapid deceleration or lugging.

he present inventionhas among its objects to rovide such a controller, namely one afior ing the desired protection and yet possessin extreme simplicity.

' A furt er object is to provide such a protective controller requiring only a sin 1e relay of simple construction to render t e controller responsive to abnormal conditions.

Another object is to provide a controller which provides for disconnection of the motor from its supply upon too rapidacceleration or deceleration-and which necessitates return of the controller to off position as a prerequisite to restarting of the'motor.

Another object is to provide a controller of the aforesaid character which provides for stopping of the motor by dynamic braking but only in the off position of the controller.

Variousv other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates diagrammatically one embodiment of the invention which will now be described.

Referring to the drawing, there is illustrated a motor M having an armature a and a shunt field f to be supplied from lines L, L and to be regulated through the medium of armature resistances R, R, R and field resistances 1', r r r, r and 1-. It is of course to be'understood that the motor might have more or lesssteps of either armature or field resistance.

The controller illustrated comprises a contact drum D, an electroresponsive line switch 1 and an electroresponsive-relay 2 in circuit with the operating winding of switch 1. Switch 1 is arranged to beenergized by the drum, but only in the'off'position of the latter, whereas said switch has auxiliary contacts 1 which establish a maintainin circuit for said switch independent of sai drum, but including relay 2. Also, as hereinafter set forth, the auxiliary contacts 1 of switch I serve to control a step of field resistance r.

The drum in of! position interrupts the motor circuit and establishes a dynamic braking circuit for the motor. Movement of thedrum in opposite directions completes the motor circuit for reverse operationsof the motor and continued movement of the tected against any fiprolonged abnormal conditions such as e ect response of relay 2, whereas the operator is penalized for his, carelessness by having to return the drum to off position in order to restart the motor. More particularly, the relay 2 has a series winding 2' in series with the motor armature and an opposing shunt winding 2 connected across the motor armature. These windings are so designed that under normal load conditions they permit the relay to remain closed. On the other hand, the series coil has a suflicient number of turns to open the relay against the opposing action of the a shunt coil under excessive current conditions in the motor circuit and the shunt coilis designed to open the relay under given voltage conditions with no current in the series coil. (For exam lo, the series coil may be designed to so unction at two times the full load current with no voltage on the shunt coil and the shunt coil may be desi ed to open the relay with double line vgt age impressed on it with no current in the series coil.) Thus the relay may be so designed that if the motor is accelerated too rapidly with consequent excessive surges of current the series coil will reponderate the shunt coil and open said relay to deenergize the switch 1, whereas if themotor is decelerated too rapidly, with cons uent excessive voltage and reverse current, t e shunt windin alone or aided by the series coil when su jected to reverse current will effect opening of the relay to deenergize switch 1. Furthermore, even though too rapid deceloration is avoided, the relay will respond if the operator reverses the motor before stopping thereof. Such reversal will subject the series coil to a high current, while the shunt coil has only a low voltage impressed thereon, with consequent res onse of the relay to deenergize switch 1. W hen relay 2 has responded as aforedescribed, it will remain open and if drum D is not returned to off position the motor is permitted to coast until the same is brought to rest while return of the drum to off position stops" the motor b dynamic braking. When the motor is brought substantially to rest either by coasting or b dynamic braking relay 2 recloses and the otor can then be restarted, providing thedrum has been returned to oil position.

Considering the controller in further detail, the drum in off position completes circuit from line L by conductor 37 to contact 16 of the drum, thence by cross connected segments 16 and 11 to cont-act 11 by conductor 38 through relay 2 by conductor 39 through the windin of switch 1 to line L. This circuit provides for energization of switch 1 and upon response of said switch its contacts 1 connect conductor 38 by conductors 40, 41 and 42 to line L thus establishing a maintainin circuit for switch 1 independent of the f relay 2.

Also, the drum in off position completes a dynamic braking circuit which may be traced from the right hand terminal of the motor armature by conductor 43 through resistances R R and R by conductor 44 to drum contact 19, thence by cross connected segments 19' and 21 to contact 21 by conductors 45 and 46 through the coil 2 of relay 2 to the left hand terminal of the motor armature. Furthermore, the drum in off position provides for energization of themotor field, the field being fully excited if switch 1 is in closed position and being weakened by the resistance 9' if said switch is in open position. This energizing circuit may be rum, but inclusive of traced from line L by conductor 42 through resistance r if switch 1 is open, and through contacts 1 if said switch is closed, by conductors 47 and 48 to contact 30, thence by relay 2 thence through the motor armature from left to right by conductor 43 through the armature resistance by conductor 44 to contact 19 by cross connected contact segments 28 and 23 to contact 13 and by conductor 52 to line L On the other hand, assuming reverse movement of the drum segments, the motor armature circuit may be traced from line L through switch 1 to drum contact 18 as al ready traced, by cross connected segments 23 and 24 to contact 19 by conductor 44 through the armature resistance and the motor armature in a reverse direction to that previously described through the winding 2 of relay 2 by conductor 46 to drum contact 12 by cross connected segments 26 and 27 to contact 13 and by conductor 52 to line L When the drum is moved in either direction into its successive positions it first excludes armature resistances R, R and R progressively and then inserts the field re? sistances 1' 7*, r r 9' and 1" progressively. hen the drum is moved to the left segments 29, 25 and 24 are engaged rogr'essively with contacts 20, 15 and 14. egment 29 is cross connected with segment 28 and hence when it engages contact 20 it shortcircuits resistance R. Segment 25 is cross connected to segment 29 and when it enga es contact 15 it short-circuits resistance TV. Segment 24 is cross connected to segment 25 and when it engages'contact 14 it short-cirouits resistance R Upon reverse operation of the drum these same segments short-circuit the armature resistances progressively in the same order. However, these segments accomplish this in the following distinctive manner. Segment24 first engages contact 19 after which segments 25, 29 and 28 progressively engage contacts 20, 15 and 14.

After the drum has been movediin either direction sufficiently far to exclude the armature resistance it disengages segment 30 from contact 30 thereby inserting resistance 9' in the field circuit, the remaining field resistances being short-cirouited by cross connected segments 31 and 36 or 31" and 36 according to the direction of movement of the drum. As will be apparent, the segments 31 to 35 and 31 to 35 are so arranged as to effect inclusion of the resistances 1', r 1", r and r progressively as the movement of the drum is continued.

What I claim as new and desire to secure by Letters Patent is:

1. The combination with an adjustable speed electric motor, of an armature resistance therefor, a manual controller for controlling said resistance to effect acceleratlon opposing control windings, one connected in series with the motor armature and another connected across the motor armature.

2. The combination with an adjustable s eed motor, of an armature resistance t erefor,'a manual controller associated with said resistance operable to effect startin and speed regulation of said motor and adapted in a iven position to effect establishment of therefor, and means responsive toabnormal conditions in the motor circuit resulting from improper operation of said controller, to disconnect said motor from its supply and to necessitate return of said controller to its braking position as a prerequisite to re starting of said motor, said means having normally opposing control windings, one connected in series with the motor armature and another connected across the motor armature.

3. The combination with an adjustable speed motor having a shunt field winding, of a manual controller operable to effect reversal, acceleration and deceleration of said motor and adapted in a given position to effect dynamic braking thereof, means responsive to abnormal conditions in the motor circuit resulting from improper operation of said controller, to disconnect said motor from its supply and to render said controller ineffective pending returnthereof to its braking position, said means having normally opposing control windings, one connected in series with the motor armature and another connected across the motor armature, and means associated with said latter means for weakening the shunt field winding of said motor upon disconnection thereof from its supply.

4. The combination with an adjustable speed electric motor, of a relay having a control winding in series with the motor armature and a control winding connected across the motor armature for modifying the effect of said former winding and a manual controller adapted'in a given position to effect dynamic braking of said motor and movable into other positions to effect starting and ynamic braking connections :speed regulation thereof, said relay being responsive to render said controller ineffective in its lastmentioned positions and necessitating return of said controller to its dynamic braking position as aflprerequisite to restarting of said motor.

5. The combination with an adjustable speed electric motor having ashunt field winding, of a relay having a control winding in a series with the motor armature and a control winding'connected across the motor armature formodifying the effect of said former winding, amanual controller adapted in a given position to effect dynamic braking of said motor and movable into other positions toeffect starting and speed regulation thereof, said relay being responslve to render said controller ineffective in its last mentioned positions and necessitating return of said controller to its dynamic braking position as a prerequisite to restartin of said motor, and means associated with said relay and acting upon res onse thereof for weakening the shunt fiel winding of said motor.

6. The combination with an adjustable speed electric motor, of a manual controller to effect acceleration and deceleration thereof, an electroresponsive switch for disconnecting said motor from its supply, said switch being responsive only upon a predetermined positioning of said controller and being adapted to maintain itself in closed position upon movement of said controller out of said predetermined position, and a relay connected in the energizing circuit of said switch, said rela having normally opposing control win in one being connected in series with tile motor armature, and another being connected across the motor armature.

7. The combination with an adjustable speed motor, of a manual controller operable to effect starting and speed regulation of said motor, and adapted in a given osition to effect establishment of dynamic raking connections therefor, an electroresponsive switch for disconnecting said motor from its supply, said switch being responsiveonly upon movement of said controller into. its

said motor, and adapted in a given position to effect dynamic braking thereof, an electroresponsive switch for disconnecting said motor from its suppl upon improper operation of said contro ler, said switch being ada ted to close only upon movement of sai controller into its dynamic braking position, and being adapted to maintain itself in other positions of said controller, a relay for interrupting the energizing circuit of said switch, said relay having a control winding connected in series with the motor armature and a modifying control windin connected across the motor armature, an means associated with said switch for weakening the shunt field winding of said motor upon opening of said switch.

In witness whereof, I have hereunto subscribed my name,

EDWIN J. GOVE. 

